1. Field of the Invention
This invention relates to a decorating pigment-transfer sheet for heat-resistant articles and a method for decorating heat-resistant articles such as ceramic articles with the transfer sheet.
2. Description of the Prior Art
Hitherto, screen printing has been generally employed for decorating surfaces of ceramic plates such as pottery plates with photographic images. Screen printing methods include a direct method and an indirect method. The direct method comprises directly applying a photosensitive emulsion onto a mesh screen composed of a metal or resin material and then forming a pattern thereon through a color-separated photographic film. The indirect method comprises forming a pattern on a film coated with a photosensitive emulsion through a color-separated photographic film, and then transferring the pattern onto a mesh screen by pressurization. In such screen printing methods, whether a direct method or an indirect method, a mesh screen having a pattern formed thereon is placed on a surface of a pottery plate, and a color pigment paste corresponding to the used color-separated film is provided on the screen. Then, the pigment paste is forced out through the screen by means of a squeezee onto the surface of the pottery plate for printing deposition. In the screen printing, such printing steps are repeated many times corresponding to the number of the desired separated colors to decorate the pottery plate with photographic color images. If a pigment-transfer sheet having photographic images should be known in the art, such a transfer sheet must be screen-printed on a sheet to provide the photographic images and similar to the conventional screen printing methods in printing effects.
In the case of a screen printing method, however, the thickness of the printed pigment becomes very thick because of the openings of mesh screens, for example, as thick as 20 to 100 microns per layer. Thus, a color of an underlying pigment paste can not be seen through an upper layer of another pigment paste having a different color and only the color of a pigment paste in the top layer is observed. Therefore, it has been impossible, for example, to produce an optional synthetic color by applying pigments of three primary colors. In order to provide natural photographic images according to conventional screen printing methods, it was necessary to prepare a large number of color-separated films from an original photographic film and to increase the number of printing screens. Thus, such a method had defects in that a large number of printing mesh screens, printing steps and pigment pastes therefor were needed to provide natural color images. Since each pigment layer is thick, the parts where pigment layers are overlapped become too thick to give unsatisfactory photographic decoration.
Such screen printing methods also have problems in that mesh sizes of the screen are restricted to certain coarse opening sizes and thus the pigment paste passing through the screen according to a printing pattern becomes relatively coarse. As a result, the resolution obtained by the conventional screen printing is about 100 lines/inch or less. Such low resolution is not sufficient for decoration with photographic images. Moreover, according to such screen printing methods, photographic images can be printed only on smooth surfaces of ceramic plates, and can not be printed on uneven rough surfaces thereof.